Ship NAVTEX: How It Works, Information Types, and Benefits
Ensuring the safety of the vessel and its crew is paramount for every mariner. Even the most cautious mariners can be subject to accidents.
From the very beginning of voyage planning, mariners need access to the latest information affecting the vessel’s route. For a vessel, the most crucial information is safety-related information, including maritime safety information.
Maritime safety information includes navigational and meteorological warnings, weather forecasts, navigational hazard warnings, missing vessel warnings, and other urgent information related to the safety of the vessel and its crew.
Due to the limitations of radio systems, continuous monitoring to extract the required information from the vast amount of information is impractical. NAVTEX automatically provides accurate information to all mariners.
NAVTEX, short for “Navigational Telex,” is a device used on ships to provide short-range maritime safety information in coastal waters automatically.
It is suitable for all types and sizes of vessels. NAVTEX has a coverage range of up to 400 nautical miles from the broadcasting station. NAVTEX receivers on ships print warnings, navigational and weather forecasts, and urgent maritime safety information for ships.
NAVTEX is a key component of the Global Maritime Distress and Safety System (GMDSS). NAVTEX automatically transmits information using radio telex or narrowband direct printing (NBDP).
How does NAVTEX work?
NAVTEX operates on the 518 kHz medium frequency (MF) band. Some countries also use 490 kHz for national language broadcasts, also known as national NAVTEX.
When MF reception is difficult, 4209.5 kHz is used for transmissions. The default setting for NAVTEX is 518 kHz. To distribute this information, the world is divided into 21 regions, called NAVAREAs (including the recently added five Arctic regions).
Each NAVAREA contains multiple NAVtex stations to facilitate the transmission of information.
SELECTION OF STATIONS
All NAVtex receivers are programmable, allowing the navigator to ensure that only information from selected NAVtex radio stations is displayed or printed.
The “Radio Selection” menu under the “Menu” option on the NAVtex receiver allows the navigator to automatically or manually select the desired radio station for reception.
In automatic selection mode, NAVtex continuously receives maritime safety information for the vessel’s area without user intervention.
If the vessel’s position data is derived from any navigational aid (e.g., GPS). The NAVtex system automatically determines the vessel’s current area of operation and selects the appropriate NAVtex radio station.
In manual mode, the navigator can select the radio station they wish to receive.
For a list of NAVtex radio stations, refer to the UK Admiralty Radio Signals List, Volume 3, Part 1, and the List of Coast and Special Service Radio Stations (List IV).
Types Of NAVTEX
NAVTEX receivers receive the following messages:
A = Navigational Warnings
B = Weather Warnings
C = Ice Advisories
D = Search and Rescue/Piracy and Armed Robbery Information
E = Weather Forecasts
F = Pilot Messages
G = Automatic Identification System (AIS) Messages (formerly DECA Messages)
H = Loran C Messages
I = Omega Messages
J = Satellite Navigation (GPS or GLONASS) Messages
K = Other Electronic Navigation Aids Messages
L = Navigational Warnings (Additional)
M through U = Alternate
V = Fisherman’s Notices
W through Y = Alternate
Z = No Message Available
NAVTEX receivers can be set to ignore certain message types. However, navigators cannot reject Class A, B, D, and L messages due to their importance.
An audible alarm may also sound when a Class A, B, D, or L message is received. This alarm can only be reset manually.
It’s also important to note that when setting the message types for reception, it’s recommended to only receive essential messages.
Otherwise, receiving broadcasts electronically will result in wasted paper or a large number of messages to browse through.
Message Format
The message format displayed on a Navtex receiver is as follows:
ZCZC b1 b2 b3 b4 Main Message NNNN
ZCZC: Start code, indicating the beginning of a message.
B1: This code indicates the station ID.
B2: This code, called the Topic Indicator, indicates the message type. (A-Z)
NAVTEX receivers use the letters B1 and B2 to reject messages from pilot-related stations.
B3 and B4: B3 and B4 represent the two-digit serial number of each message.
NNNN: Indicates the end of a message.
Receivers use the letters B3 and B4 to avoid repeating previous messages.
The following is an example message:
ZCZC OA20
WZ 1593
West Coast of Scotland
North Cardinal Light Buoy 58.01.2N 005.27.1W
Permanently withdrawn.
WZ 1562 Cancelled
NNNN
All NAVTEX messages contain relevant information in the header. In the above message:
The letter “O” indicates a transmission from a NAVTEX station, in this case, Radio Portpatrick.
The letter “A” indicates a marine warning message.
The number “20” indicates the priority of the marine warning message.
Advantages of having a NAVTEX receiver on board:
NAVTEX provides an additional layer of safety and peace of mind. It conveniently monitors maritime warnings, weather alerts, search and rescue alerts, and other data, suitable for vessels operating 200 to 400 nautical miles from the coast. It provides relevant navigational and meteorological information in real time.
Because the NAVTEX receiver automatically receives information, it is extremely convenient to use. The crew member on duty does not need to monitor the information regularly or be present at specific times.
Furthermore, there is no need to reset the receiver. This saves time and reduces distraction for the crew on board.
Based on the information received by the NAVTEX receiver, the voyage plan can be modified to meet the vessel’s safety needs.
The crew member on duty can respond to any nearby distress alerts. He or she can also check the weather forecast and plan accordingly. Therefore, a NAVTEX receiver is an indispensable part of the navigational equipment on the bridge.
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NAVTEX Receiver Checklist
Every officer must ensure that there are always sufficient rolls of NAVTEX paper on board.
Always ensure that the receiver is fully stocked to avoid missing any important information.
It is recommended to keep the NAVTEX receiver powered on at all times to avoid missing important information that could affect the vessel’s navigation.
Ensure the operating instructions are available on the bridge.
A plastic copy of the sea/mining areas the vessel may pass through (labeled with NAVTEX stations, their coverage areas, and times) should be kept with the device.
A useful manual covering programming, status, and self-test procedures can be created and kept with the device.
Tests should be performed regularly to verify device performance. Extreme care must be taken to avoid confusion between the programming of the B1 code (station indicator) and the B2 code (message type). All SOLAS-certified vessels must be equipped with a NAVTEX system. NAVTEX is a compact yet powerful device that provides safety information and can be customized to suit the needs of each user.
